Using the picture below, select the number that shows where the citric acid cycle occur in the mitochondria. 1 2 3 4

To identify where the citric acid cycle occurs in the mitochondria, we need to review the structure of the mitochondrion. The citric acid cycle, also known as the Krebs cycle, takes place in the mitochondrial matrix.

Understanding Mitochondrial Structure

1. Outer Membrane: The outer layer that contains various proteins, including porins.
2. Inner Membrane: Highly folded (forming cristae) and is where the electron transport chain occurs.
3. Intermembrane Space: The space between the inner and outer membranes.
4. Matrix: The innermost compartment where the citric acid cycle occurs.

Conclusion

Given the question asks for a selection from the options provided (1, 2, 3, 4), the correct answer would correspond to the "Matrix" of the mitochondrion, represented by option 3.

Thus, the number that shows where the citric acid cycle occurs in the mitochondria is 3.